Its one licence per household regardless of the number of computers or their operating system.
Try thing out for yourself.
Download from https://infinitekind.com/download-moneydance-personal-finance-software
Downloaded version of Moneydance is a full working version with the only limit being a maximum of 100 manually entered transactions, with no time limit. Imported files from other financial programs and your bank have no limit on imports. If you decided to purchase you are sent a key by email that unlocks the 100-manual transaction limit. If after testing with this free trial version you purchase and change your mind there is a 90 day money back guaranty.
For the future Moneydance never sunsets the version it releases. So, you don’t have to upgrade. If you won’t to upgrade the next version is free (say 2015 to 2017) and from then on you get a 50% discount. All upgrades within a version are free.