Bebo has moved closer to Facebook despite earlier joining Google's new alliance OpenSocial, which is seen as the new threat to Facebook's success.
Michael Birch, co-founder and chief executive officer of Bebo, said its decision to introduce "interoperability" with had been made because launching stand-alone platforms had become a confusing "pain in the butt for everyone" using the site.
The open application platform, the first to be compatible with Facebook's own applications platform, will allow brands to extend their widgets to other social networking sites.
Bebo has signed up more than 40 digital companies, associations, retailers and media companies for the launch, including Flixster, Gaia Online, Pocketbook, Wallop and YouthNoise.
According to Birch, Bebo intends to work with Google on its OpenSocial application platform, which launched on November 1, but had been concentrating on developing its links with Facebook in the meantime.
Bebo said it plans to integrate with Google's OpenSocial, which is currently not compatible with Facebook, by early next year. Google has so far signed up MySpace and Bebo for its own cross-platform initiative.
Birch said: "By opening up our API and establishing an open developer-friendly platform, we enable developers big and small to create entertaining, engaging applications for our global community -- providing another great way for Beboers to communicate, relate and express themselves online."
Adam D'Angelo, chief technology officer at Facebook, added that the deal meant developers could extend their brand reach, which will allow for further application development that "will ultimately benefit both Bebo users and Facebook users".
In November, Bebo unveiled its Open Media strategy, which has effectively extended the site from traditional social networking into a multimedia entertainment portal.
Bebo Open Media, which has signed up Channel 4, ITN and the BBC to provide online video and news content paves the way for ad-funded programmes that can be viewed wholly online.