I find it hard to believe that Billard GL isn't a typo. I thought it was called 'billiards'? Oh well - maybe not in Germany, where its developers are from. This is a very pretty and very vacuous pool sim. The physics are probably mostly fine, although they seem a little wonky at times. Everything else is sub-par.
The UI is horrid (but simple!). You can change one aspect of your view by moving the mouse while the left-button is held, and another aspect by doing the same with the right button held. But in 'View' mode, they're totally unworkable and oddly unpredictable, and in 'Aim' mode, they're usable, if barely, but a complete pain in the ass.
As near as I can tell, you always hit the ball dead-center, so english was impossible to achieve; I tried angling the camera up and down to get top/bottom-spin, but couldn't see that it ever had any effect. So right from the get-up, you have an unworkable camera control system, and a clunky and simplified aiming system.
My complaints don't stop there! There's no network-play support, which isn't necessary but would have been nice. There's also no shot-calling mechanic so the rules are simplified as well, compared to what I play 'down the pub'. Playing single-player is only doable via 'Training' mode, so there's no AI opponent which, honestly, I can understand. Trying to implement one would probably be a hellacious task, and this is open-source hobbyist development.
As installed, there is no functional sound. The configuration menu mentions it, but according to the website it's just a 'dummy' option, as sound support hasn't been implemented yet.
There's just nothing this game does that Yahoo! Pool doesn't do better, outside of the graphics. For the record, while very simple, the graphics are pretty sharp both literally and figuratively. Billard GL is a functional game, but just barely, and it's not pleasant to play. I should mention that it does appear to be playable completely via the keyboard, but manipulating the camera via keyboard controls is even more painful than using the mouse.