Yes. There are very few restrictions on what you can do with Suneido. There are no fees or additional licenses required to use or distribute Suneido. The C++ source code for the Suneido executable itself is under the Gnu Public License (GPL). This means that if you include Suneido in your package, you must either include the source code or make it available. And if you modify or add to the C++ code, you must make your modifications available, also under the GPL. Any code you write in Suneido however, is yours - you can do whatever you like with it and it does not have to be under the GPL. For specifics, read the license.