Is owning a Buddha statue, having it displayed in a Jewish home, considered a transgression of idolatry, technically speaking?
Buddhism is fully considered Avodah Zara (Foreign Worship/Idolatry), as the practitioners of the faith frequently bow to their Buddha statues, and even offer it incense. Clearly, this is the literal definition of idolatry and thus it is assur to have a statue of the "Buddha."
It is a clear idol, and even if the statue might not have been worshipped, it contains strong Touma (as it was created for the purpose of meditational-worship) and should not be kept at any house and rather destroyed.
There are a few different possible problems which much be addressed. The verse (Shemos 20:20) states "You shall not make [images of what is] with me; gods of silver and gods of gold you shall not make for yourselves". Based on this verse the Gemara (Rosh Hashana 24b) says that it is prohibited to make any image of man or celestial bodies (sun, moon,or stars). This is a Torah prohibition. The Shulchan Aruch (YD 141:4) rules like this Gemara, that is prohibited to create these images.
The next question is when someone else made these images, and now you own it. May you keep such an image or must you get rid of it? The Gemara(ibid) says that even if someone else made these images you may not keep it as it will lead to "chashada" a suspicion. The concern is that others will think you are serving these images. This halacha is a Rabbinic prohibition and is brought as practical halacha in Shulchan Aruch (ibid).
This seems to be precisely our case and as such it would seem be prohibited.
The Chochmas Adam (86:6) says that since this halacha is based on the suspicion that a person is serving these images and since today that is very uncommon, there is no problem to keep an image of a man. (This Chochmas Adam, is one of the reasons that many observant homes have dolls for children to play with). However the Chochmas Adam says that an image which people do serve even today, there of course would be a prohibition to own. That would certainly be true in this case. It is very important to note that the Chochmas Adam did not permit something the Torah prohibits. The prohibition to create an image of a man is true even today, even if no one serves such images.The Chochmas Adam only permitted the Rabbinic prohibition of keeping such an image, on the basis that the concern that it will appear that you serve the idol is no longer true. Many authorities do argue on the Chochmas Adam.
Another issue over is if this statue was used for idol worship, it would be prohibited to benefit from, unless there was nullification by the one who served it.It is possible, but one would have to know the details of how you got it to comment on that.