2. Open Source Development Challenges
Kevin P. Fleming
Director of Software Technologies
Digium, Inc.

3. Ground Rules
A thorough understanding of all protocols and services being used is mandatory; FOSS products tend to expose the complete details of the system, rather than 'packaging' it for the user
FOSS telephony products tend to be 'toolkits' or 'platforms', which can be used in many ways but don't come preconfigured to act in any particular way
Using FOSS products in your telephony network will be challenging, rewarding, fun and frustrating all at the same time!

4. Project Management FOSS projects run on 'Internet time'
Bugs are usually fixed quickly, unless obscure
Features are added when someone feels like coding/testing them
Many projects have commercial enterprises involved who can develop and add code for a fee
Code (especially development code) can change radically in a short time period, making developing add- on products a challenge

5. Lifecycle FOSS projects have widely varying release cycles
Backwards compatibility is not always preserved
Documentation lags code releases (sometimes by many months)‏
Major new features that you contribute may not appear in an actual release for an extended period
Bug fixes (especially security issues) are frequently the driving force for minor releases

6. Licensing Concerns
Most FOSS projects use GNU General Public License version 2 (or similar)‏
Contributors retain copyright to their code
Code cannot be used with or linked to non-GPL code without exceptions being granted
Code cannot be incorporated into commercial product without complying with GPL or obtaining alternative license

7. Support Google is your best friend!
Mailing lists, IRC channels, web sites/wikis
Paid support available for many projects
Consultants specialize in specific areas and can provide a great deal of configuration/development assistance
Urgent support requests will fall on deaf ears in most cases... using FOSS projects means you need to be very self-sufficient