It's Valve who need to implement this to the Linux Steam Library, OOO has nothing to do with this.

You can already download the game from OOO website and make it run on Linux

Using Steam means you have to wait for Valve to implement the game, the coding in the game is the same. Linux only has to interpret a java-code game, running through Valve platform. Which (again) is out of OOO reach...

Steam != OOO

Steam = Valve

Valve went to Linux, not OOO... Valve is bringing everyone along the way, and games like CoD BO2 have more demands than Spiral Knights... So programmer are focusing on major title rather then F2P games that are not related to their company.

Yes Valve focused to bring TF2 on Linux, it's their baby, not Spiral Knights

Edit: You should try making a Thread on Steam rather than OOO website... Steam (Valve) has a lot of networking to do and a lot of tweaking already made scripts and sequences. They have to connect you to OOO server via Valve network passage and OOO has to recognize the linux/steam data.

There's a lot more going on then just "insert game here"