Can I still make this software using Open Street Map data as a paid service on the Internet?
And if I decide to use data from the Open Street Map project, will I have to release all my source code with the Creative Commons license?
Thanks!
As far as source code goes, you only need to release your source if you use and modify the actual OSM rendering engine source code. Your code used to display maps (rails, django, php code whatever) is your own and won't be "compromised" by using software licensed in even a restrictive open source licensing scheme.
An example using my site: I plan on using OSM for parts of ridewithgps - I will make money by selling accounts that have special features shown on an OSM map. So, that person can print or redistribute the maps according to the Creative Commons, but I won't lose "value" because features my business model relies on revolve around performance analysis of their own data, not displaying something on the map.
If your business model is making topographical trail maps and selling them, using OSM data, then you will may have a barrier to success: anyone can print out the map and distribute it freely or for money, regardless of whether it was made through your site or not.
They also have a number of mailing lists, including a legal one intended to address questions such as yours which can be found here: http://wiki.openstreetmap.org/wiki/Mailing_list