In 1905, Zamenhof re-published the sixteen rules of grammar, in combination with a "universal dictionary" and a collection of exercises, in a work entitled Fundamento de Esperanto (Basis of Esperanto). At the first Esperanto World Congress at Boulogne in the same year, a declaration was issued, including the following (shown here in intentionally literal translation):
"The only, once-and-for-all binding on all Esperantists, basis of the language Esperanto is the little work "Basis of Esperanto", in which nobody has the right to make a change. If anyone deviates from the rules and models given in the said work, he never can justify himself with the words "thus desires or advises the author of Esperanto". Every idea, which cannot be conveniently expressed by that material, which is found in the "Basis of Esperanto", each Esperantists has the right to express in such a manner, which he finds the most correct, in the same way as is done in every other language. But for the complete unity of the language to all Esperantists it is recommended to keep imitating as much as possible that style, which is found in the works of the creator of Esperanto, who has worked the most for and in Esperanto and best knows its spirit."
On the basis of Zamenhof's declaration that an international language is "common property" (which was also made in the Boulogne declaration, but in a different section to that quoted above), it is possible to draw some comparisons between Esperanto and what would today be called an Open source project. However, the comparisons are limited, because a key part of the open source philosophy is an almost complete freedom to make modifications. The context of declaration of the language as "common property" was that Zamenhof was abrogating his personal rights and privileges as its creator; the language itself remained subject to substantial controls on its modification, as shown above.