Yes, you can use more than one open source software component in your proposal and project.
The following is the excerpt taken from the competition website:
Project Implementation:
"Participants can make use of any APIs (Application Programming Interfaces)
that are not proprietary from any commercial products."
In addition, it is also stated in the competition's website, the usage of supporting open source software should be clearly definied in the proposal.

- Language : PHP
- Web server : Apache
- Database : MySQL
Participant is free to make use of any open source software to participate in the competition. The combination of open source software which mentioned above are all acceptable but are not exhaustive.
The following is the related excerpt taken from competition's official website:
Project Implementation:
Participants are encouraged to make use of open source software
(either ready or to be created by participant), to produce a workable solution.
The usage of supporting open source software should be clearly stated in the proposal.
