I've invested so much time into this that it's difficult to just let it go.
Also, I was actually able to sell a non-exclusive license to the source code 6 months ago, which further discouraged me from opening it up as it would be nice to make back some more of the time I've invested in S+.
However, I will never charge for S+. It will always be free for anyone to use.
If the time comes where I cannot maintain S+ or no longer have the desire to, I will open source the code.