It appears to me that the citation in LSJ from Plutarch's Romulus for "runaway slave" being a meaning of apostatēs might be incorrect. I think that the word that is translated for apostatēs is "fugitives"; the word for "slaves" in the sentence occurs 2 words earlier -"oiketōn." I post both the English and Greek of Romulus below, from the Logos Perseus resources.
LSJ:
ἀποστάτης [τα], ου, ὁ, deserter, rebel, ἀ. τοῦ βασιλέως Plb.5.57.4, cf. Wilcken Chr.10 (ii b.c.), Plu.Cim.10; seceder, SIG705.41,50 (Delph., ii b.c.).
II. runaway slave, Plu.Rom.9; ἀ. κύων runaway dog, Id.2.821d.
III. Lat. apostata, apostate, Cod.Theod.16.7.7. ἀποστᾰτικός, ή, όν, of or for rebels, rebellious, θράσος Plu.Rom.7. Adv. -κῶς, ἔχειν to be ready for revolt, Id.Pel.15: Comp. -ύτερον, φρονούντων PLond.2.354.6 (i. b.c.); -κῶς πράττειν τοῦ λόγου Chrysipp.ap.Gal.5.406. II. disposed to exfoliate, of bones, Hp.Fract.25, Antyll.ap.Orib.6.1.6. III. Rhet., belonging to ἀπόστασις b.1.6; -κόν, τό, Hermog.Id.1.10; σχήματα ibid., Aps.p.259 H.; λόγος Eust.1389.28. Adv. -κῶς Id.635.58. ἀποστάτις [τᾰ], ιδος, ἡ, pecul. fem. of ἀποστάτης, ἀ. πόλις Lxx1Es.2.18, AJ11.2.1.
Plutarch - Romulus 9 [2] But perhaps it was necessary, now that many slaves and fugitives gathered about them. either to disperse these and have no following at all, or else to dwell apart with them. For that the residents of Alba would not consent to give the fugitives the privilege of intermarriage with them, nor even receive them as fellow-citizens, is clear, in the first place, from the rape of the Sabine women, which was not a deed of wanton daring, but one of necessity, owing to the lack of marriages by consent; for they certainly honoured the women, when they had carried them off, beyond measure.
[2] ἦν δʼ ἴσως ἀναγκαῖον, οἰκετῶν καὶ ἀποστατῶν πολλῶν ἠθροισμένων πρὸς αὐτούς, ἢ καταλυθῆναι παντάπασι τούτων διασπαρέντων, ἢ συνοικεῖν ἰδίᾳ μετʼ αὐτῶν. ὅτι γὰρ οὐκ ἠξίουν οἱ τὴν Ἄλβην οἰκοῦντες ἀναμειγνύναι τοὺς ἀποστάτας ἑαυτοῖς οὐδὲ προσδέχεσθαι πολίτας, ἐδήλωσε πρῶτον μὲν τὸ περὶ τὰς γυναῖκας ἔργον, οὐχ ὕβρει τολμηθὲν ἀλλὰ διʼ ἀνάγκην, ἑκουσίων ἀπορίᾳ γάμων· ἐτίμησαν γὰρ αὐτὰς ἁρπάσαντες περιττῶς.
Also, Logos morphologically tags ἀποστατῶν as being a nominative masculine singular participle from the verb apostateō instead of the noun apostatēs.
Unfortunately, I can't report this as a "typo" so this is the way I'm bringing attention to this.