@mevaqesh brought a few sources on the subject
Rav Shmaryahu Yosef Chaim Kanievsky brings the sources of this part of the Rambam's halacha in his book Kiryas Melech:
Mesehta Kala Rabisi chapter 1
ברייתא מכאן אמרו עשרה כממזרים ואינם ממזרים ... בני מפותה
...גמ'] בני מפותה סופן שמפתין לבן
part of the list of 10 who are similar to mamzerim, are the sons of a seduced woman, the gemorah explains what will happen to them is that they will be seduced by a boy (man)
the list of the "10 mamzerim" is also brought in Pirkei Rabbeinu HaKadosh 10:3
and in mishnas Rabbi Elazar 18 in the list of the children of the nine midos (which is different then the list in the Shulchan Arch 240.3
but there sons of a seduced woman are defined as: when a man has relations with his engaged (kedushin) wife to be while she was still in her father's house and without a kesuba.
this Rambam is also brought by the Ungvarer Rebbe Menashe Klein (about him in hebrew (chabad)) in the book Mishneh Halachos part 12:301 (text version) in his answer about ~ "what is the problem with walking with a girl and talking to her to check if she is good for him to marry"
where he brings this Rambam and proves that the "seducing" in this Halacha does not mean that the man had relations with her but only that he convinced the girl to marry him.
it seems his option on Jewish dating is that
1. the man can look on the girl if he wants to check if she is disgusting to him, once he checked he can not look again,
2. it is good if the girl is shy from the man like Rivka did when she fell of the camel (http://www.sefaria.org/Genesis.24.64),
3. no convincing of the girl is permitted, only we ask her if she wants as they did by Rivka (http://www.sefaria.org/Genesis.24.57)
and not (the nonjewish way), as shechem did to Dina (Rashi Beraishis 34.3)