GPL and GNU Library General Public License

only for RuBoard - do not distribute or recompile

GPL and GNU Library General Public License

IMP is distributed under the GNU Public License (GPL), which I've described in Chapter 5, "PHP." The horde libraries that IMP uses are distributed under the GNU Library General Public License (LGPL). The LGPL is a variant of the GPL with an important restriction lifted. A copy of the LGPL library is included in this book.

Under the GPL, any code you write that links to code that is written under the GPL falls under the GPL. This can be undesirable in some cases. You might have a portion of your system that is a trade secret. In this case, linking with GPL code would force you to open up your code.

Under the LGPL, you can link your code with the code covered under the LGPL without causing your code to fall under the GPL or LGPL. This allows you to have trade-secret software that uses publicly available libraries. The customer has access to the source code of the libraries. Your source code can stay hidden.

Use of IMP Under the GNU Public License

You are free to sell media that contains IMP, but you must provide a way for the customer to get the source code. Any modifications you make to IMP must be passed to a customer at their request if you sell IMP on a disk to that customer. You can provide a for-fee service using IMP. You can provide a free service with IMP. You can put IMP on as many computers as you choose without paying royalties. You can sell computers that have IMP installed. You can modify IMP to suit your needs.

For example, suppose you were to modify IMP to add some very interesting feature. Let's assume this feature is rotating banner ads at the bottom of each message. You also packaged it so that it was a single-click install. You could sell the program at any retail store. You would have to either include the source code on the disks you sold or give the customer the ability to obtain the source code. After users buy the package, they could copy it, give it to anyone and install it on as many machines as they want. They can also copy and modify the features you added to IMP.

You could also start a Web-mail “based email service and charge users a nominal fee for use. Companies that provide Web-based email usually support themselves through advertising and offering extra services beyond a minimal level for a charge.

only for RuBoard - do not distribute or recompile