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From Wes Wannemacher <w...@wantii.com>
Subject Re: [OT] POM, licenses and dependency trees
Date Tue, 03 Mar 2009 23:59:09 GMT
On Tuesday 03 March 2009 15:40:43 stanlick wrote:
> If you look at the POM for Struts 2.1.6 there are many more dependencies
> than what show up running
> dependency:resolve.  I verifies the default for scope because several of
> the dependencies are "test."   It appears the default is all scopes, so I
> am wondering why I don't see them all when I run dependency:resolve.
>

There are a few things to keep in mind here Scott, Java is not like C. If you 
have a compiled binary, the executable is linked to it's required libraries, 
whether you use them or not. Then, if you try to run the executable and one of 
the libraries is not available, the program will crash. In Java, there is a 
difference between compile-time and run-time dependencies. Java programs will 
only seek out it's required classes when they are used. Because of this 
behavior, libraries like Struts typically have many compile-time and unit-
test-time dependencies that do not need to be satisfied at run-time. If you 
are using struts2-core w/o any plugins, the list of dependencies is 
(purposely) small. Add the spring plugin and the dependencies grow, add 
hibernate, etc. etc. 

On licensing, it is messy, but here are a few thoughts - 

1. Nearly all of the (F)(L)OSS licenses are more concerned with distribution 
than usage. I've used GPL licensed software in many commercial projects, but 
the software was used, rather than distributed. This is perfectly acceptable, 
you only have to become concerned when you want to distribute (i.e. sell) the 
software. Since we are mostly web-app developers, we are generally writing 
software that our customers use, but we are rarely concerned about the 
distribution of the software.

2. To keep things straight, there are different families of license. Most OSS 
licenses fall into one of only a few categories. There is the GPL which 
basically states that if you plan to use it in a distributable project, you 
need to plan on making your source GPL licensed as well. The ASF style license 
is much less restrictive, IMO, this is why you often see things like Apache 
HTTPD distributed with commercially licensed software like Solaris. The Apache 
license really only has a few requirements... You have to include a copy of 
the Apache license if you distribute Apache licensed software, you can't use 
the Apache trademarks, you have to attribute apache - 

http://www.apache.org/foundation/licence-FAQ.html#WhatDoesItMEAN

There is also the BSD family of licenses which basically allow you to do as 
you please. You can sell it if you'd like, but you have to retain copyright 
notices and the warranty clause. 

There are a few other popular licenses, the Mozilla license and Eclipse 
license come to mind. 

The big thing is to consider what you plan to do. If you want to sell the 
software you are creating, you want to make sure that your dependencies' 
licenses allow it. 

If you don't plan to distribute your source, then you are usually safe. 

-Wes
-- 

Wes Wannemacher
Author - Struts 2 In Practice 
Includes coverage of Struts 2.1, Spring, JPA, JQuery, Sitemesh and more
http://www.manning.com/wannemacher


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