That link is not a source, it is a link to a website showing sources for software. Don't enter the
http://iappcat.com/apps/list?search=text+twist as a source, just click on it. You will get a page listing all the different sources that have that particular program on their source. Then select one (as I did by picking the top one) Click the blue name of the program, this opens a second page. There will be another blue link next to the word "repository" Click that and it will give you the URL to enter into installer as the source. The top one in the list is one with a repository starting with grmillergr and it works. Hope that helps.