I don't have any experience with LIRC, but it appears to support learning:
If you can't find your remote control here it does not mean that your remote control is not supported but there is no config file for it yet. All remote controls that are supported by learning remote controls, i.e. almost any, should also work with LIRC. Please send me your config file if you add a new remote control.
Based on that quote from the LIRC site, it appears that the absence of any Outlaw files is because nobody's ever written (or at least never shared) a setup. You would just need to learn the commands from your 990's remote. The 990's commands should be easily accepted (I've learned them to both an
MX-500 and an
MX-700 , and others have learned them to Harmony and Pronto remotes).
I don't know how the learning process works under LIRC, but it's pretty simple with the MX series remotes I've used. I actually prefer learning commands myself over downloading someone else's config file because I can organize functions the way that I want them.