there is plenty of software for controlling x10. But.....not alot of software to control the cm15.
if you go to the main page of this forum and look down the page you will find third party programs along with other main programs. I think you just overlooked it.
there is open source software but there again i haven't been able to find any that would support the cm15 very well.
The main reason alot of users are having problems is with their setup. There are alot of variables in any kind of home automation system. Powerline noise, range or rf, phase problems. And most all of these problems can be fixed by using noise filters, antenna mods, different rf receivers, and a good phase coupler and maybe a x10 amplifier.
The software has its own issues but if you can fix all the hardware problems then the software problems are minor. IMHO I have tried several x10 programs and ALL have their own ups and downs. And if you have hardware problems or noise or phase issues then no software in the world is going to get you up and running.