spmod3 not free right?
no you have to pay 0.05 BTC for it - just do the math what you can mine a day with open source and what with sp - the difference has to re-finance that 0.05 BTC in short time - maybe in few days mining SIGT is not profitable anymore (at current rate there are already much better coins to mine).
which coin is much better than SIGT?
just keep your eyes open, i stopped mining SIGT 3 days ago when diff went up to fast and mine now for $ 6-7 per 1070

(like i did with SIGT the first 2 days) - with SIGT i would mine now for just slightly above $ 2 per 1070 and this i could also make with the major currencies - SIGT is now better profit with trading it.