The first quarter of 2008 was the most successful quarter in history in terms of open source vendors raising venture capital funding, with the amount raised hitting $203.75m, up from $100.40m in the same quarter of 2007.

Yes, it is 1 April, and no I’m not joking. Following the plunge in the fourth quarter of 2007, VC funding started 2008 on a high.

Here’s the stats run down:

• The amount of funding in 1Q08 just beat the previous record, of $193.7m, set in 4Q06.
• There were 20 open source funding deals announced in the quarter, beating the previous record of 17, set in 1Q05 and 4Q06.
• Of those 20 funding deals, 17 had a disclosed value, giving an average deal size of $11.99m.
• That is the second highest average deal size ever, behind the $13.84m recorded in 4Q06, when there were 14 deals with a disclosed deal value.
• In comparison, there were 11 deals with a disclosed value in the first quarter of 2007, giving an average deal size of $9.13m.

Well that’s the good news. Despite the vast improvement, there is reason for caution, however, especially when it comes to the proportion of funding invested in Seed and Series A deals, which represents the pipeline for further investment.

There were just three Seed or Series A deals with a disclosed value announced in the quarter, totaling $9m, meaning disclosed Seed/Series A deals represented just 17.65% of the deals and 4.42% of the funds raised in the quarter, both record lows.

Although the likes of Ringside Networks, Bluenog and Engine Yard did prove there is more to come in the future, the vast majority of the funding raised in the quarter went to more familiar names, such as Automattic, Greenplum, SugarCRM, and Pentaho.

In fact, so many of the old names raised funding in the first quarter, it’s difficult to see where significant further funding will be raised in the coming months unless a few more start-ups emerge

It is also worth noting that the majority of the funding raised in the first quarter was announced in January. We already noted the extraordinary number of deals announced in the first month of the year. In total, 10 deals with a disclosed value totaling $142.9m were announced in January (a record, suffice to say), followed by five deals totaling $49.35 in February, and two deals totaling $11.5m in March. The downward trajectory is evident.

Despite the incredible growth in the first quarter in total, it is based on that statistic that I’m predicting that that total funding in 2008 will be higher that the $323.87m raised in full year 2007 but still well below the $546.3m raised in 2006.

UPDATE - Mark Radcliffe has a unique insight into open source funding thanks to the fact he acts as legal adviser to many open source firms and is general counsel of the Open Source Initiative. He thinks we are heading for another record year and points out that seed funding is hard to track. - UPDATE

Incidentally, total funding to date stands at $2.64bn.