[k1e]

Looks very similar to another open-source prototyping tool:

http://pencil.evolus.vn/

https://github.com/evolus/pencil

[xmichael999]

pencil kicks ass, blows omnigraffle out of the water and you don't have to find with omnigraffle every few weeks when they do an update and claim again that your license is invalid or pirated!

[big_chungus]

And funny, just did a search and found a cracked copy in under a minute. Looks like that DRM really works...

It's like the "pls no pirate" messages on DVDs that pirates never see.

[sbarre]

For what it's worth, I'll share my counter-anecdote.

I've never once had a license problem with Omnigraffle and I've been a paying customer for 10+ years.