Can one use the Felo program for other sports, too?
Yes, one can, however, Felo doesn't work well with team sports. Moreover, sports that are ended after a certain amount of time doesn't work well either.
As far as team sports are concerned, Felo isn't usable at all if you have a group of people, and on every training day, you compose two completely new teams out of it. The only possible situation is a set of teams rather than people. Every team can be treated like one fencer in a Felo file. This limits Felo heavily in team sports, especially for leisure sport groups.
As far as sports with time limit are concerned, you can only use the three possible results 1:0, 0:1, and 1:1 for win, loss, and even. However, I don't know a sport with time limit that isn't a team sport at the same time.
For all other sports with a sportsman vs. sportsman bout like tennis, badminton, table tennis, arm wrestling, and staring contest, there shouldn't be problems. If there is no real score but only winner and loser, see above, in all other cases you simply put the result in the Felo file.
By the way, it is not very important whether you count single point, (tennis) games, or sets. It won't make much difference. For example, in tennis you may record a 6:4 6:3 either as 2:0 or as 12:7. (If you have too much time, you may even count the single points.) On the other hand, the more information, the better.