So the Damascus Document refers "the Way" and "the New Covenant" in a place called Damascus, expects a singular Messiah with priestly and royal aspects to come in the Last Days, believed in eternal life, cited similar OT verses (like the fallen tent of David) that are found in the NT, held the concept of "being called by name," which is also found in the NT (e.g., James 2:7 and throughout Acts), held a concept similar to the Primal Adam that is found in later Jewish Christian writings, expected to "see His Salvation" (yeshua) at the end of time, and altered the OT to support the inclusion of gentiles (or nilvim) into the movement. And these are only some of the similarities between the DSS sect and Jewish Christianity. There are more.
Regarding the meaning of nilvim (or "joiners") as gentiles, not only is this how the word understood in the OT (and in an eschatological context), this meaning is confirmed by the statement that follows a few lines later: "And with the completion of the Era of these years, there will be no more joining to the House of Judah, but rather each man will stand on his own watchtower" (CD 4:10-12).
And while Bauckham in the link I gave earlier notes that "the Qumran community and the early Christians ... are the only two groups we know to have applied the image of [the Way] to their own way of life," he avers that, "The first Christians did not practice Qumran halakhah or anything like it," and I do not agree with this.
For example, 1QS col. 5 says:
"...he shall undertake by the Covenant
to separate from all the men of falsehood who walk in the way of wickedness. For they are not reckoned in His Covenant.
They have neither inquired nor sought after Him concerning His laws that they might know the hidden things in which they have sinfully erred; and matters revealed they have treated with insolence ... Likewise, no man shall mix with him with regard to his work or property lest he be burdened with the guilt of his sin. He shall indeed keep away from him in all things; as it is written, Keep away from all that is false.
No member of the Community shall follow them in matters of doctrine and justice, or eat or drink anything of theirs, or take anything from them except for a price; as it is written, Keep away from the man in whose nostrils is breath, for wherein is he counted?
For all those not reckoned in His Covenant are to be set apart, together with all that is theirs."
And according to Paul, "When Cephas came to Antioch, I opposed him to his face, because he stood condemned.
For before certain men came from James, he used to eat with the Gentiles. But when they arrived, he began to draw back and separate himself from the Gentiles because he was afraid of those who belonged to the circumcision group.
The other Jews joined him in his hypocrisy, so that by their hypocrisy
even Barnabas was led astray (Gal. 2:11-13).
This is at least
something like Qumran halakhah, and also illustrates the inclusion of gentiles into Jewish Christianity ("even Barnabas was led astray").
Another example would be that both the DSS sect and Jewish Christians were pro-Torah. As 1QpHab col. 7-8 puts this (interpreting the same OT verse, Hab. 2:4, that Paul uses to support his doctrine of faith in Rom. 1:17 and Gal. 3:11 to opposite effect): "'And the Righteous shall live by his faith.' Its interpretation concerns all
Doers of the Torah in the House of Judah, whom God will save from the House of Judgment because of their
works and faith in the Righteous Teacher."
Vermes translates the word "works" as "suffering," but the word in Hebrew, amal, has the sense of labor/toil/work:
http://biblehub.com/hebrew/5999.htm
As James 2:10-14 puts it, "For whoever keeps the whole law and yet stumbles at just one point is guilty of breaking all of it ... What good is it, my brothers and sisters, if someone claims to have faith but has no works? Can such faith save him?"