Building a community around open-ended questions like this is next to difficult. SE was able to counter this because of the nature of the allowed questions. A website with the premise of "ask programming questions that do not have a specific answer" lacks the specificity to cultivate a community that is connected enough to be lively (based on my small amount of experience with forum management).

SE is in a good position to attempt such a thing because the community already exists.

However, it may still face issues with liveliness.

It may be a better idea to just allow these sorts of questions with a specific tag (and visual indicator on question links).

I imagine it providing a way for people to pose potential problems/questions, and either letting users post their suggestion/opinion of how the problem should be solved. Rosetta Code limits itself to programming problems, but this hypothetical site could allow more general questions/challenges as well.

2. http://www.reddit.com/r/programming/ is a terrific discussion forum for for all programming-related topics.