When you publish a ModelMaster on ParametricParts, you can choose what license you use. While anyone can generate 3d models from your ModelMaster, your license controls whether others have access to the source code for the ModelMaster, and how they can use it.
With Parametric Parts, authors will Always have full rights to the ModelMasters they create.
You are free to distribute, share, remix, and this work commerically, as long as you attribute your use to its author.
You can use, transmit and use this work commercially, if you attribute your work to the author. You may remix, alter, or build upon this work only if you publish your work under a similar license
Anyone can build models using your script, but no-one has access to see, modify, or copy the script. Keep in mind that you cannot use this model if it is a derivative of any share-alike style license.
You have unlimited rights to use the model script as you choose, and in addition you are granted unlimited rights to download and build the model without authenticating ( subject to volume rules )