It's (probably) not illegal.

If you do it in the manner you describe, you are not using the Font Software, which would be copyrighted.

You also shouldn't even mention the name "Catull" anywhere, because that is trademarked.

The typeface, i.e. the style of the glyphs, could be design patented, but a) I doubt that Catull is and b) this has never been tried in court. Despite the myriad of obvious plagiarisms of popular typefaces.
Because it would be a mess.

Arial and Helvetica are very close. There are diffences though. Now someone needs to define how many differences a font would need to be considered disinct? Does every letter have to show some distinction? If so, how many variations of 'o' can there realisitically be? But if not all letters must be distinct, how many can be the same - 10, 20?
And what is distinct? Can I just take a typeface and change its width to 99%? Can I just in-/decrease the font weight by 2%?

Once design patents on fonts start being enforced, the life of font designers would turn to hell. Because they're all just producing minor variations of the same Latin Alphabet. It would be next to impossible to create a new text typeface and not run into infringement problems.
And nobody wants that.

Thus, nobody has ever been sued over plagiarising a typeface. The only court cases I'm aware of were against companies who used the Font Software, ie. the .ttf of .eot or whatever, which is an obvious copyright violation.

Everything else is just FUD by font designers.

I'm not Swiss either. I'm a Syrian national currently living in Germany, but I've lived in The Netherlands, The U.K. and Norway and if all goes well, I'll be living in Indonesia soon.

Have you read the source you linked?
It's actually one big opinion piece.

And KAPITEL III § 4 reads:

"Copyright protection of text typefaces is denied by majority academic opinion."

I.e.: nobody has ever actually tried it in court, hence there are no verdicts, but law academics predominantly doubt it would work.

You will also notice when you read the Licence Agreements of fonts, e.g. from Monotype or Linotype, they -at least those I have cared to read...- only deal with the FONT SOFTWARE, never the typeface.

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I agree that very fancy presentational typefaces COULD enjoy some sort of design patent protection, but with millions of fonts based on the Latin alphabet in the wild, it's gonna be tough not to run into some sort of prior art. The more extravagant your font gets, the more likely it would hold up in court.

Text fonts, however, have no chance at all. The differences between Helvetica, Frutiger, Lucida, Arial ... they are so small. If you wanted to patent the design, you'd have to speciy what made them special. Why your modifications weren't trivial, or obvious. You'd also have to state what the "Base" is, i.e. what is the "Natural Form" of the Latin Alphabet from which you derived you work. Adrian Frutiger might make a case for his uppercase Q, but who's to say that is not what a Latin Q is supposed to look like?

Boy, don't pretend you have any kind of academic education. If you had, you could contribute to a discussion with facts and not just a slew of ad hominem attacks.

I have provided multiple sources now that clearly point you out as dumb.

Educate yourself or leave this conversation.

Good grief, people...

http://blog.crowdspring.com/2011/03/font-law-licensing/
http://nwalsh.com/comp.fonts/FAQ/cf_13.htm
http://intellectual-property.lawyers.com/intellectual-property-licensing/Company-Sues-Over-Unauthorized-Use-of-Its-Fonts.html

Now find me a source that contradicts me.

Before you post any more smilies, read this:

http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=UNESCO_Font_Lic
http://en.wikipedia.org/wiki/Wikipedia:Public_domain#Fonts

Typesfaces are not copyrightable in the US and most other countries. You can apply for a Design Patent, though I would reckon the number of fonts on this website that are patented is under 1%.

And unless your typeface is very original, don't expect a design patent to hold up in court. Lucida is patented, but they haven't done anything against millions of sans-serif typefaces that look the same, probably because Lucida looks hardly any different than earlier typefaces like Arial, Helvetica or Frutiger.

There have only been two prominent trials in this area. Both revolved around the infringing companies copying the font-files and just renaming and/or manipulating them. That is illegal because of the "software" aspect of fonts.

But if a font designer sits down and just imitates a font, there is just about nothing you can do. Because the shape of letters is fundamentally dictated by the Latin Alphabet. You can't claim monopoly on that.

Typefaces aren't copyrightable in most countries, including the United States.

If you acquire the copyright to a font, you only acquire the copyright to the font-FILE, (the .ttf or .eot or what have you), because they hilariously qualify as computer software.
People can still imitate the TYPEFACE though, i.e. the design of the font. That's why every successful font has numerous clones under different names (as names of fonts/typefaces are of course trademarkable).

You might be able to acquire a design patent or trade dress to a font in specific combinations of colors, shapes and such, i.e. as part of a logo. So, for example, you can use the Catull typeface as you please, but using it in blue, red, green and yellow letters would very quickly infringe on Google's logo trademark.