There are a number of good Open Source licenses at the Open Source Initiative. You would be best served by starting with one of those as a base and not trying to write your own from scratch.
It is very important that you include the standard non-indemnity clauses, such as this one from the MIT license:
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
It would be good to stipulate non-erasure of copyright notice. If you have your name and email address in a copyright notice in every source file then you might at least get some advertising leverage from the pirates. A salaried programmer who works for a boss who violates copyright will usually leave the copyright notices in the source code.
If your software is any good people will copy it, in whole or in part, mangle it, and include it in their commercial products without notifying you or paying you anything. These infringements will never get to court because you wont be able to detect them. Welcome to life as we know it on this planet.
Your best protection is to offer downloads from an attractive site that offers your own commercial support for the software, and to publish updates from time-to-time, and to respond to email inquiries. Having well-known software is in itself a deterrent to violations.
